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I () HOW \KD. I nlofnologut .nd Chief of Burr.u 




V. II. CHITTENDEN, s« . D.. 

I top am/ Stored Pro 


I.. 0. Howard, Entomologist and Chief of Bureau. 
C. L. Marlatt, Entomologist and Acting Chief in Absence of Chief . 

R. S. ('UPTON, Knculin Assistant. 

\V. F. Tastet, Chief. Clerk. 

F. H. Chittenden, in chargt of truck crop and store/ ■product ins,ct investigations. 

A. I». Hopkins, in charge of forest insect investigations. 

W. D. Hunter, in charge of southern field crop insect investigations. 

V. M. Webster, in chargt of cereal and forage insert investigations. 

A. L. Quaintance, in churn, of deciduous fruit insect investigations. 

E. F. Phillips, in chargt of bet culture. 

I). M. Rogers, in dung, ,,j prevt nting spread of moths, field work. 

Rolla P. Currik. in charge of editorial work. 

Mabel Colcord, in charge of library. 

Truck ('nor and Stored Product [nsect [nvestioations. 

F. II. Chittenden, in charge. 

II. M. Russell, C. H. Popenoe, Wm. B. Parker, II. 0. Marsh, M. M. High, 
Fred A. Johnston, D. E. Fink, John E. Graf, A B. Duckett, entomological 

I.J. Condit, collaborator in California. 
W. X. (Inn, collaborator in Oregon. 
THOS. II. JoNES, collaborator in Porto Rico. 

Marion 'I'. Van Horn, Pauline M. Johnson, Anita M. Ballinger, preparalors. 

ADDITIONAL COPIES of this publication 
-£*- may be procured from the Superintend- 
ent or Documents, Government Printing 
Office. Washington. D. Cat S cents per copy 

Circular No. 162. 

United States Department of Agriculture, 


1 O HOWARD 1 ' ■ ■" ul Chief of Hureau. 


/■- . / i /.ill 

I || Qhittbnden, Si D 

I \ i i:< iin ( n >t:i . 

For m;iii\ years the potato-tuber moth, known scientifically as 

Phthorimxa opercuhlla Zell., has I n the worsj potato pesl in 

California. Ii has now reached the State 
,.i' Washington and menaces adjacent 
States. This insecl feeds also upon to- % 
mato, eggplant, and tobacco, which 'I" 
not. a rule, suffer much injury. 
When ii occurs on tobacco ii is known as 
the splitworm. 

The mature moth of this species, which 
is quite small and grayish in color, is 
shown in 6gure I, a; the Ian a is shown in 
b and c; and the pupa in </. Si/..'- are in- 
dicated by the size lines in the figure. 

The eggs mas be laid upon the le&\ es oi i 


■ ■[.) 


*3L i — ~*-~2* 

It is believed thai there 

on other part- of the plant-, and the mi 

ante caterpillars or worms quickly bore 

between the surfaces of the leave- or into 

the potatoskin, which they mine in every 

direction, finally devouring the exterior. 

are two or more generations in the course of a summer, and certainly 

another one can be produced in store. It tint- happen- that tlusmsecl 

belongs to both truck-crop and stored-producl insecl pests. 

An example of injury by this species to potatoes is shown in figure 
_>. At a isasection showing the eggs at the top; at h, a badly mfesti d 

I will 

in' . 

THE l'OTVio I iki.i: MOTH. 

potato in section; at the left is a section containing two pits, (Zand 
/, in which the larva lias been at work, while at l> and c are shown 
t he egg, highly magnified. 


This species is widespread in its distribution, but in this country, 
mil il the present year (1912), we did not know of its rapid dissemina- 
tion. Abroad it is well known in Hawaii, all portions of Australia, 
New Zealand. Algeria, and many other countries, including southern 
Europe. As an enemy to tobacco it has been known for several 
years in Florida and in North Carolina, South Carolina, and Virginia. 1 

The directions for applying remedies 
which follow are for the benefit of per- 
sons inquiring in regard to means of 
control. Which of these should be 
used can be best determined by trial in 
the different localities under the differ- 
ent conditions in which the insect ex- 
ists. This applies especially to the 
question as to the. best material for 
iumigat ion. 


As evidence of the importance of the 

pest a few ([notations or notes should he 
r <t Mr. J. E. Graf, working under the 

Fig. 2.- Work of the potato-tuber moth: o, direction of the writer, wrote: 
Section of tuber, showing eye and eggs 

deposited about il; 6, egg in outline; e, In September. 1012. ail unusual outbreak of 
egg, lateral view; ,/,/, mines of larva in this pest occurred at El Motile, (al., due entirely 

to a combination of circumstances. Thousands 
of acres of potatoes were planted in southern Cali- 
fornia— many more than the market would stand. 
This meant that the market was continually clogged and the prices were poor, so that 
the crop was worked off very slowly. The tuber moth (Pkthorimeea operculella) is 
always found here, but the crop is generally handled so quickly and carefully that small 
loss results. This year, however, careless work and the leaving of potatoes in the 
ground too long have given tile insect a tremendous start, and now its ravages are 
greater than ever before. A combination of the moth and low prices has so discouraged 
many of the growers that they are Leavingtheir potatoes to rot. ami as these are becoming 
infested there will be a great number of moths wailing for the fall potatoes. * * 

Later, September 17, 1912, Mr. Graf wrote in regard to this species 
that two growers near El Monte, Cal., lost Slid. not) and 870,000, 
respectively, on potatoes that year. Items of this kind show the 
necessity of investigating the problem. 

potato, a, Natural size; 6, c, greatly en- 
larged; d, somewhat reduced. (Redrawn 
from Riley and Howard.) 

i it is somewhat doubtful if the splitworm on tobacco ami the potato-tuber moth are the same insect, 
although they appear to !«• identical according t" the best authorities on the subject. This is a matter to 

be settled later. 

I ill P0TAT0-T1 BED M"i H. 8 

le from numerous similar complaints, including the usual nun, 
ber from California for the pasl two years, this species has been pi 
ceivetl from Eagle Lake and Hallettsville, Tex ; San Jo* Co ta Rica; 
- attle Auburn, and Yakima, Wash. ; New"} ork City, where it hat not 
become acclimatized so far as known; Fort Collins, Colo : and Lari- 
morc, V Dak. These records include onlj occurrences on potato. 

In the case of the lasl report the tuber moth was 9tated to have 
been imported into southern California in potatoes from China. It is 
doubtful if the species has been introduced into North Dakota, but 
inquiries have been made in regard t<> the danger of it- being intro 
duced there as well as into Minnesota and some other Stati 

M I nil s 

The potato-tuber moth is a difficull insect t" control. It i- nol 
possible it) reach the tuber wofms in their mines in the potatoes or in 
the stalks or tubers growing in the Geld, which make- it neccssan to 
proceed against the pesl l>\ other methods. Of these, several must be 
emplo) ril to insure buc< i 

The first measure consists in the maintenance "I clean methods <>f 
cultivation. This implies that all infested potato plants and solana- 
ceous weeds, such as ground cherry, bull nettles, horse nettles, and 
vol u nt err potato plant-, gro^ ing in the same vicinity as the potatoes, 
must be destroyed. This can be done by prompt burning as soon 
as insect infestation is manifest. The burning of the weed- will 
eliminate places for the breeding of the insect or for its successful 
hibernation. Domestic animals such as sheep and hogs are valuable 
for the destruction of remnant- and may be utilized l>\ merely turn- 
ing them into the field. 

Crop rotation, as in mosl other cases of insect injury, is desirable 
w here possible, and the cooperal ion of all potato growers of the neigh- 
borhood i- practically a necessity. In certain cases, as, for example, 
in a county where many potatoes are grown, it mighl l>e |><>--il>le l>\ 
legislat ion to enforce the discontinuance of potato planting for a year, 
requiring at the same time the destruction of the weed- which serve as 
I'ood plant-. There are several alternate food crops which do not 
suffer materially from this insect. About the best of these are 
Leguminous crop-, like beans, peas, cowpeas, alfalfa, and clover. 
These possess a dual value, as the) all ad as soil restorers. Sugar 
beets, celery, and crucifers are also good as alternate food crops. 
Grains may serve in the same way, as they are not attacked by the 
tuber moth. Care in digging i- ad\ isable in order not to cut into t he 
tuber or leave dug potatoes in the field over night where reinfestation 
coidd occur. 

II MM, \I1'"N 

^hile all of these remedies are of value, the best remedj i- the 
fumigation of infested tubers u ith bisulphid of carbon or hj drocj anic- 

4 j II K I'll I A I ti- I I'KKl; MOTH. 

acid gas. If bisulphid of carbon is used, it should be at the rate of 
3 pounds to 1,000 cubic feel of air space, including the potatoes; 
1 ounce to a barrel of 96 pounds' capacity would not be excessive. 
With an exposure of not more than 2 l hours, no harm should be done 
to the potatoes for planting. The bisulphid should be evaporated in 

Fig. 3.— Fumigator used for stored products infested by insects. (Author's illustration. ) 

tins, like pie plates, and a cover should be placed on the top of the 
fumigating barrel or box so as to make it as nearly air-tight as possi- 
ble. At the end of 24 hours the potatoes should be removed, placed 
in a fresh barrel, and closed up. 

Where it can be conveniently done hydrocyanic-acid gas should 
be used in a specially constructed fumigator (see fig. 3), also Lras- 

I ill P01 HO ii in i: \l'»i ii. 

tight. In ill'- case of bisulphid of carbon there i-^ great danger in 
bringing the chemical into proximity i" fire, Buch as a lighted lantern 
or cigar, for the gaa is 1 1 1 ■_•■ 1 1 1 v inflammable and even explosive. Thin, 
too, the bisulphid-of-carbon method costs Blight!} more than tin- 
bydroc} anic-acid-gas method. 

Fumigation with hydrocyanic acid :_ r a>, properh performed, is 
nol dangerous, but it improperl} performed is decidedly dangerous 
to human and other animal life, a> the fumes are ven poisonous and 
me deadh when inhaled in an\ amount. This gaa i-> more penc 
trating than bisulphid of carbon and can !><• used l>\ an intelligent 
person without trouble, it he first familiarizes himself thorough!} 
with the procedure by careful!} studying the printed directions or 
assisting some one who has bad experience in this work. The cubic 
contents <>l* the receptacle t" be fumigated, on which is based the 
amount of chemicals to l>e used, can be readil} computed. 

i ii i i n\8TH \ i)l \ ii mil . 

A building, box, or room (see fig. 3) of about 100 to 200 bushels' 
capacity suitable for the fumigation of a quantity of potatoes would 
contain about 500 cubic feet. A fumigator of 1 1 1 i— cubic capacity 

might In' built 8 feet square b\ 8 feet in height. A _ r I, and perhaps 

the best, means of preventing the escape of the gas would be to line 
the fumigator with sheet tin, with soldered joints, and over sheathing. 
Another method would be to sheath the room inside, cover the walls, 
ceiling, and floor with tarred or heav} building paper, with joints 
well lapped, and cover the inside with matched ceiling boards. The 
fumigator should always be equipped with a tight door in which the 
joints have been broken, similar to the door of a refrigerator or safe, 
and should (lose with two refrigerator catches against a thick felt 
w.athcr >tri|>, which should render it practical!} gas-tight. Thus 
constructed it would furnish sufficient space for the fumigation if 
about 200 bushels of material. There would also be sufficient spaoe 
for the application and diffusion of the hydrocyanic-acid gas, 1 carbon 
bisulphid, or other fumigant from the top with a charge more than 
necessary for the quantity of potatoes treated. 

Approved : 

James Wilson, 

?< cretary <>f A<p u ultun . 

Washington, D. C, September SO, 1912. 

i a rh hydi 
anyone who requests It, stating that il ed f- >r the potato-tuba n 



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